There has been proposed an image forming apparatus such as a laser printer, in which a toner cartridge is detachably attached to a developing device.
For example, JP-A-1-219865 discloses a toner replenishment apparatus, in which a toner cartridge is detachably attached to a developing unit in the image forming apparatus. A toner replenishment port is opened in the bottom of the toner replenishment apparatus. A toner accommodated in the toner replenishment apparatus drops from the toner replenishment port and is supplied to the developing unit.
In the toner replenishment apparatus, a first shutter unit is disposed in an upper part of the toner replenishment port. A second shutter unit is disposed in a lower part of the toner replenishment port i.e., the outside of the toner replenishment apparatus.
The first shutter unit includes a rotatable rotary shutter. The rotary shutter closes the toner replenishment port from the upper side when a top cover of an image forming apparatus body is in an opened state in a state where the toner replenishment apparatus is attached to the image forming apparatus. As the top cover changes to a closed state, the rotary shutter rotates so as to open the toner replenishment port from the upper side.
The second shutter unit includes a slidable slide shutter. The slide shutter opens the toner replenishment port from the lower side by sliding as the toner replenishment apparatus is attached to the image forming apparatus while the slide shutter closes the toner replenishment port from the lower side in a state of detaching the toner replenishment apparatus from the image forming apparatus.
The toner replenishment apparatus of JP-A-1-219865 doubly disposes the shutters with respect to the toner replenishment port in order to prevent the toner from leaking from the toner replenishment port. However, the toner may leak from the toner replenishment port due to an influence of vibration by opening and closing at the time of opening and closing the slide shutter outward arranged in the toner replenishment apparatus.